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Handling overflows in gas_for_mem calculation

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This commit is contained in:
Tomusdrw 2016-01-17 13:47:16 +01:00
parent d58879ef76
commit 83ac4bce06
1 changed files with 31 additions and 11 deletions
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42
src/evm/interpreter.rs
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@ -465,7 +465,7 @@ impl Interpreter {
},
InstructionCost::GasMem(gas, mem_size) => match mem_size {
RequiredMem::Mem(mem_size) => {
let (mem_gas, new_mem_size) = self.mem_gas_cost(schedule, mem.size(), &mem_size);
let (mem_gas, new_mem_size) = try!(self.mem_gas_cost(schedule, mem.size(), &mem_size));
let gas = overflowing!(gas.overflowing_add(mem_gas));
Ok((gas, new_mem_size))
},
@ -473,7 +473,7 @@ impl Interpreter {
},
InstructionCost::GasMemCopy(gas, mem_size, copy) => match mem_size {
RequiredMem::Mem(mem_size) => {
let (mem_gas, new_mem_size) = self.mem_gas_cost(schedule, mem.size(), &mem_size);
let (mem_gas, new_mem_size) = try!(self.mem_gas_cost(schedule, mem.size(), &mem_size));
let copy = overflowing!(add_u256_usize(&copy, 31));
let copy_gas = U256::from(schedule.copy_gas) * (copy / U256::from(32));
let gas = overflowing!(gas.overflowing_add(copy_gas));
@ -485,21 +485,24 @@ impl Interpreter {
}
}
fn mem_gas_cost(&self, schedule: &evm::Schedule, current_mem_size: usize, mem_size: &U256) -> (U256, usize) {
fn mem_gas_cost(&self, schedule: &evm::Schedule, current_mem_size: usize, mem_size: &U256) -> Result<(U256, usize), evm::Error> {
let gas_for_mem = |mem_size: U256| {
let s = mem_size >> 5;
s * U256::from(schedule.memory_gas) + s * s / U256::from(schedule.quad_coeff_div)
// s * memory_gas + s * s / quad_coeff_div
let a = overflowing!(s.overflowing_mul(U256::from(schedule.memory_gas)));
let b = overflowing!(s.overflowing_mul(s / U256::from(schedule.quad_coeff_div)));
Ok(a + b)
};
let current_mem_size = U256::from(current_mem_size);
let req_mem_size_rounded = ((mem_size.clone() + U256::from(31)) >> 5) << 5;
let new_mem_gas = gas_for_mem(U256::from(req_mem_size_rounded));
let current_mem_gas = gas_for_mem(current_mem_size);
let req_mem_size_rounded = (overflowing!(mem_size.overflowing_add(U256::from(31))) >> 5) << 5;
let new_mem_gas = try!(gas_for_mem(U256::from(req_mem_size_rounded)));
let current_mem_gas = try!(gas_for_mem(current_mem_size));
(if req_mem_size_rounded > current_mem_size {
Ok((if req_mem_size_rounded > current_mem_size {
new_mem_gas - current_mem_gas
} else {
U256::zero()
}, req_mem_size_rounded.low_u64() as usize)
}, req_mem_size_rounded.low_u64() as usize))
}
fn mem_max(&self, m_a: RequiredMem, m_b: RequiredMem) -> RequiredMem {
@ -1100,7 +1103,7 @@ fn get_and_reset_sign(value: U256) -> (U256, bool) {
fn set_sign(value: U256, sign: bool) -> U256 {
if sign {
(!U256::zero() ^ value).overflowing_add(U256::one()).0;
(!U256::zero() ^ value).overflowing_add(U256::one()).0
} else {
value
}
@ -1121,6 +1124,23 @@ fn address_to_u256(value: Address) -> U256 {
U256::from(H256::from(value).as_slice())
}
#[test]
fn test_mem_gas_cost() {
// given
let interpreter = Interpreter;
let schedule = evm::Schedule::default();
let current_mem_size = 5;
let mem_size = !U256::zero();
// when
let result = interpreter.mem_gas_cost(&schedule, current_mem_size, &mem_size);
// then
if let Ok(_) = result {
assert!(false, "Should fail with OutOfGas");
}
}
#[cfg(test)]
mod tests {
use common::*;
@ -1149,7 +1169,7 @@ mod tests {
let mem_size = U256::from(5);
// when
let (mem_cost, mem_size) = interpreter.mem_gas_cost(&schedule, current_mem_size, &mem_size);
let (mem_cost, mem_size) = interpreter.mem_gas_cost(&schedule, current_mem_size, &mem_size).unwrap();
// then
assert_eq!(mem_cost, U256::from(3));